This invention relates to a filter, in particular to a filter for cleaning the lubricating oil of an internal combustion engine.
The lubricating oil of an internal combustion engine under certain operating conditions contains moisture or water. Water or moisture arises in the combustion of the fuel-air mixture and can pass into the oil plan with the blow-by gases. There it is carried with the oil through the oil pump among other things to the oil filter. In particular under unfavorable climatic conditions, i.e., in the event of very low outside temperatures, this water can freeze and occlude a filter element or a valve for a short period of time. As a result, the motor is not adequately supplied with oil during a cold start and therefore it can be destroyed.
Known from DE 42 43 217 is a liquid filter, in particular a lubricating oil filter which has a filter body 13 which can be replaced. Within the filter body, two valves are arranged. The valves are a pressure relief valve and a check valve. Such valves ordinarily comprise a rubber valve member which fits against a metal valve plate. These valves are extremely reliable, but nevertheless there is a danger that under extreme operating conditions, in particular low temperatures, functional disturbances can occur.
Known from JP 5/118 448 is a multifunctional filter in which a high corrosion resistance and a high resistance to wear are intended to be realized. In this filter, there is a valve of polytetrafluoroethylene, which is supposed to have the aforementioned characteristics.
It is the object of the invention to provide a filter, in particular for cleaning the lubricating oil of an internal combustion engine, whose movable parts are not only non-wearing and corrosion resistant, but also function reliably under extreme operating conditions. This object is achieved by the invention as described and claimed hereinafter.
The substantial advantage of the invention is that a valve arranged in the filter has a valve member which is coated, for example, with polytetrafluoroethylene. In addition, the contact surface of the valve can be coated with polytetrafluoroethylene or another hydrophobic material. It is also possible to manufacture the valve member of silicone or silicone-coated material. At low ambient temperatures at which there is a danger that water which may be present in the filter will form ice, the coating of the valves prevents the valve members and contact surfaces from fusing together. This means that the valve will open immediately during a cold start of the motor even at very low temperatures and in the presence of the formation of ice.
Specifically a coating of metal parts with a hydrophobic material has the advantage that on the one hand, the stability of the valve is ensured and on the other hand the surface of the component is corrosion resistant, low wearing, and functionally reliable.
Alternatively or supplementally to the special configuration of the valve, there is also the possibility of arranging a cold conductor (posistor) element in the area of the valve or in the area of the filter. This cold conductor element, or possibly also a heating head, which is supplied with an appropriate voltage, causes a rapid warming of the valve and thus a thawing of any existing layers of ice so that the valve will be operational immediately following starting of the motor.
It is furthermore advantageous to configure the contact area between valve members and contact surface in such a way that it is minimized. Also through this measure the response behavior of the valve, i.e., the ease of opening and closing at extreme operating conditions is ensured.
These and additional features of advantageous further developments of the invention are found in the description and the drawings as well as in the claims, with it being possible for the individual features to be realized individually or jointly in the form of subcombinations in embodiments of the invention and in other fields and with such features representing advantageous embodiments which can be protected as such and for which protection is claimed here.